Go to Chapter 7 of A Smarter Way.
Note the example:
total_cost = 1 + 3 * 4
You’ll recall from grade school that in equations like this, multiplication (or division) is done first, then addition (or subtraction).
To change this, use parentheses (parens):
total_cost = 1 + (3 * 4)
You can embed parens inside other parens, too:
total_cost = ((2 * 4) * 4) + 2
Go to http://www.asmarterwaytolearn.com/python/7.html and review the exercises.